Need volatile keyword for automatic variables?

Hi,

I am working with  C28346 DSP and now migrating my code from CCS v3.3 to CCS v5.   

A code which runs well in CCS v3.3 shows strange behaviour in CCS v.5.  After spending one day, I found that problem comes from matrix multiplication function:

void mat_mat_mult(float **m1, float **m2, float **mout, int n, int p, int m)
{
	int i, j, k;

	for(i=0; i < n; i++)
	{
		for(j=0; j < m; j++)
		{
			mout[i][j] = 0.;
			for(k=0; k<m; k++)
			{
				mout[i][j] += m1[i][k]*m2[k][j];
			}
		}
	}
}

Obviously, above code runs ok in Debug mode.  But it malfunctions in Release mode with any optimization, -o2,-o3

So I declared index variable 'k' as volatile with some suspicion :

	volatile int k;

Then it runs OK.  I don't understand why I should  put volatile keyword in automatic variable.  

As far as I know, valatile is declared for a variable shared by several threads.

 But an automatic variable is used only in fuction.

Followings are  code I tested to mulitipliy two matrices A=[1 2; 3 4] and B=[5 6; 7 8].

In order to make code simple, multiplication code is modified to use 2-dim array. 

The answer is C=[19 22; 43 50];  But in Release mode, it gave me C=[21 24; 35 40];

Is there any compiler option to suppress the volatile declaration for automatic variable?

void main(void)
{
	float A[2][2], B[2][2], C[2][2], C[2][2];

	A[0][0] = 1;	A[0][1] = 2;
	A[1][0] = 3;	A[1][1] = 4;

	B[0][0] = 5;	B[0][1] = 6;
	B[1][0] = 7;	B[1][1] = 8;

	mat_mat_mult(A,B,C,2,2,2);
}

void mat_mat_mult(float m1[][2], float m2[][2], float mout[][2], int n, int p, int m)
{
	int i, j;
	int k;                          // need to declare volatile,	volatile int k;

					
	for(i=0; i < n; i++)
	{
		for(j=0; j < m; j++)
		{
			mout[i][j] = 0.;
			for(k=0; k<m; k++)
			{
				mout[i][j] += m1[i][k]*m2[k][j];
			}
		}
	}
}